1. Field of the Invention
The present invention relates to outer coating substrates for electronic components, for example, piezoelectric oscillators, and piezoelectric resonant components including the outer coating substrates. In particular, the present invention relates to outer coating substrates for electronic components which are constituted by laminating various material layers, and piezoelectric resonant components using the outer coating substrates.
2. Description of the Related Art
In electronic components, for example, piezoelectric oscillators, outer coating substrates made of ceramics have been widely used to protect electronic component elements.
For example, a piezoelectric resonator 101 shown in FIG. 10 is disclosed in Japanese Unexamined Patent Application Publication No.4-4604. In the piezoelectric resonator 101, outer coating substrates 103 and 104 are laminated on the top and bottom of an energy trap piezoelectric resonant element 102. The outer coating substrates 103 and 104 are made of alumina obtained by low temperature calcining. Ceramics, for example, alumina, is superior in strength. However, manufacturing costs are high due to high calcining temperatures. It is disclosed in Japanese Unexamined Patent Application Publication No.4-4604 that the calcining temperatures are lowered to reduce the manufacturing costs.
On the other hand, a crystal oscillator shown in FIG. 11 is disclosed in Japanese Unexamined Patent Application Publication No.9-208261. In this disclosure, the crystal oscillator 112 is sealed in a package composed of a base member 113 and a cap member 114. The base member 113 and the cap member 114 are made of a glass-ceramics composite so that calcining at a low temperature of about 800xc2x0 C. to 1000xc2x0 C. is described as being possible.
Furthermore, a composite layer ceramic component shown in FIG. 12 is disclosed in Japanese Unexamined Patent Application Publication No. 10-106880. In this disclosure, low dielectric constant layers 121 and 124 are arranged as outermost layers, and the low dielectric constant layers 121 and 124 are made of a mixed material of ceramic powder and amorphous glass. High dielectric constant layers 122 and 123 are arranged between the low dielectric constant layers 121 and 124. It is described that characteristics of capacitors, resonators, and other electronic components, which include conductor layers 125 and 126, are improved by the high dielectric constant layers 122 and 123.
The outer coating substrates 103 and 104 of the piezoelectric resonator described in Japanese Unexamined Patent Application Publication No.4-4604 can be calcined at a relatively low temperature. However, the contraction rate during calcination is large. Therefore, it has been a problem that the dimensional precision of the outer coating substrates 103 and 104 is insufficient.
On the other hand, a glass-ceramics composite is used in the structure described in Japanese Unexamined Patent Application Publication No.9-208261 and in Japanese Unexamined Patent Application Publication No.10-106880. The glass-ceramics composite can be calcined at a low temperature. However, the contraction rate during calcination is large also, and the precision of substrate dimension has been insufficient.
In order to overcome the problems described above, preferred embodiments of the present invention provide an outer coating substrate for an electronic component that is arranged to be calcined at a low temperature, and to achieve greatly improved dimensional precision. In addition, preferred embodiments of the present invention provide a piezoelectric resonant component having an outer coating substrate that is arranged to be calcined at a low temperature and is superior in dimensional precision, while also being low cost.
According to a first preferred embodiment of the present invention, an outer coating substrate for an electronic component includes a multi-layered substrate having a first material layer and a second material layer laminated together, wherein the first material layer is sintered in a liquid phase and the second material layer is not sintered at the sintering temperature of the first material layer.
In one preferred embodiment of the present invention, the first material layer is preferably made of glass or glass-ceramics.
It is also preferable that the first material layer does not contain a component that dissolves into a wet plating bath.
Also, a concave portion is preferably formed on at least one major surface of the substrate.
The outer coating substrate preferably has at least one pair of capacitive electrodes, arranged to interpose at least a portion of the second material layer, and a capacitor is defined by the pair of capacitive electrodes.
In other preferred embodiment of the present invention, a resistive element and an inductance element are preferably provided in the outer coating substrate and are made of a resistive material and a magnetic material.
In another preferred embodiment of the present invention, at least two layers of the first material layer are laminated with the second material layer in the substrate.
According to another preferred embodiment of the present invention, a piezoelectric resonant component includes a piezoelectric resonant element and first and second outer coating substrates laminated on the top and bottom of the piezoelectric resonant element, wherein at least one of the first and second outer coating substrates includes a multi-layered substrate having a laminate structure having a first material layer that is sintered in a liquid phase and a second material layer that is not sintered at the sintering temperature of the first material layer.
In one specific example of the preferred embodiment described in the preceding paragraph, the piezoelectric resonant element is an energy trap piezoelectric resonant element, and the first and second outer coating substrates are laminated on the piezoelectric resonant element so as to define a space that allows for free and unhindered vibration of resonant portion of the energy trap piezoelectric resonant element.
In another preferred embodiment of the present invention, a concave portion is preferably provided on a surface of at least one of the first and second outer coating substrates, so as to define a space that allows for free and unhindered vibration of resonant portion of the energy trap piezoelectric resonant element.
It is preferred that the first material layer is made of glass or glass-ceramics in this preferred embodiment of the present invention.
It is also preferred that the first and second outer coating substrates do not contain a component that dissolves into a wet plating bath.
In at least one of the first and second outer coating substrates, at least one pair of capacitive electrodes is arranged to interpose at least a portion of the first material layer, and a capacitor is defined by the pair of capacitive electrodes.
Also, in at least one of the first and second outer coating substrates, a resistive element and an inductance element are preferably provided and include a resistive material and a magnetic material, respectively.
In addition, at least one of the first and second outer coating substrates preferably has a plurality of the first material layers.
According to various preferred embodiments of the present invention, a piezoelectric resonant component includes a package substrate, a piezoelectric resonant element fixed on the package substrate, and a junction member fixing the piezoelectric resonant element to the package substrate, wherein the Young""s modulus of the package substrate is less than a Young""s modulus of a piezoelectric material constituting the piezoelectric resonant element.
In such a preferred embodiment of the present invention, the package substrate is preferably a multi-layered package substrate having at least two layers.
The multi-layered package substrate preferably includes a first layer having a Young""s modulus that is greater than the Young""s modulus of the piezoelectric material, and a second layer having a Young""s modulus that is less than the Young""s modulus of the piezoelectric material.
The second layer having the smaller Young""s modulus is preferably made of a composite material of amorphous glass and ceramic powder, and the second layer having the greater Young""s modulus is preferably made of Al2O3 or MgTiO3.
The piezoelectric resonant element is preferably an energy trap piezoelectric resonant element having a piezoelectric plate, and a resonant portion partially provided on the piezoelectric plate.
Piezoelectric resonant components according to various preferred embodiments of the present invention are possible to be formed as components having various structures according to the aforementioned piezoelectric resonant element, the package substrate, and the junction member.
In a preferred embodiment of the present invention, package substrates are preferably laminated on both sides of the piezoelectric resonant element so as to allow for free and unhindered vibration of the piezoelectric resonant element.
Furthermore, a cap is preferably joined to the package substrate in order to surround the piezoelectric resonant element fixed on the package substrate.
The package substrate preferably has a concave portion to accommodate the piezoelectric resonant element, and, furthermore, a cover member is preferably fixed to the package substrate to close the concave portion.
Other features, characteristics, elements and advantages of the present invention will become more apparent from the detailed description of preferred embodiments thereof with reference to the attached drawings.